A polarizing plate used in the liquid crystal display or the like is a laminated body of a polarizer and a protective film.
As the polarizer constituting the polarizing plate, a film obtained by having iodine or diachronic dye adsorbed to the film made by a casting method of polyvinyl alcohol and drawn in a boric-acid solution is usually used.
On the other hand, as a protective film constituting the polarizing plate, triacetyl cellulose film is widely used. However, the triacetyl cellulose film is poor in moisture resistance and gas barrier performance, therefore the film is insufficient for the durability, heat resistance, mechanical strength and the like of the polarizing plate.
In order to improve durability and heat resistance of the polarizing plate, use of a protective film other than triacetyl cellulose film is proposed. For example, in Patent Document 1, use of a laminate film comprising a norbornene resin layer and a resin layer with a small haze value as a protective film is proposed. And to obtain a polarizing plate by affixing this protective film with the face of the norbornene resin layer faced with a polarizer containing polyvinyl alcohol is described.
Patent Document 2 proposes a protective film with a small photoelastic constant in which a resin layer having hygroscopicity smaller than that of triacetyl cellulose and a positive photoelastic constant and a resin layer having hygroscopicity smaller than that of triacetyl cellulose and a negative photoelastic constant are laminated. And a polarizing plate obtained by affixing this protective film onto a polarizer containing polyvinyl alcohol is disclosed.    [Patent Document 1] Japanese Patent Laid-Open No. 2005-115085    [Patent Document 2] Japanese Patent Laid-Open No. 2000-206303